The invention relates to a medical instrument for coagulation of tissue, comprising an electrode carrier and, at a distal end of the electrode carrier, an electrode that can be supplied with high-frequency current.
Such medical instruments are used, for example in the field of minimally invasive surgery, during a laparoscopy intervention in order to obliterate tissue. The medical instrument is guided through a trocar into an opening in the body of a patient, such that the electrode that can be supplied with high frequency current and is arranged at the distal end of the electrode carrier comes into contact with the tissue to be coagulated and obliterates this tissue.
A medical instrument for coagulation is known, for example, from the company brochure of Karl Storz GmbH & Co., Tuttlingen, “Karl Storz-Endoskope, Laparoskopie”, 5th edition, 1/2005, page 182. A medical instrument provided with product number 37370 SC is known from this brochure.
The known medical instrument has an electrode carrier in the form of a coagulation/suction tube, on the distal end of which a tubular electrode made of metal is arranged. At its proximal end, the electrode carrier can be supplied with high-frequency current via a connector piece arranged on a coupling. During the intervention, a suction line can also be joined to the proximal end of the electrode carrier designed as suction tube, such that, for example, blood or fluid is suctioned away from the operating site in the proximal direction.
A disadvantage of this medical instrument is that, during tissue coagulation, contaminants in the form of burnt tissue, for example, deposit themselves on the outer face of the electrode acting as coagulation surface, as a result of which the electrode, over the course of time, is covered with these often tenaciously adhering deposits. These contaminants adhering to the electrode form an insulating layer on the metal electrode surface, such that the effective coagulation surface area of the electrode is reduced or completely eliminated and no longer comes into contact with the tissue to be obliterated. As a result, the medical instrument is unsuitable for further use.
A further disadvantage is that the electrode of the medical instrument covered with contaminants can only be cleaned outside the patient, such that the medical instrument has to be withdrawn from the opening in the patient's body and, after cleaning or replacement of the electrode, has to be inserted back into the opening in the patient's body. This increases the time taken to perform the medical intervention.
Another medical instrument is known from document DE 33 90 567 C2 which is a bipolar coagulator having an electrode at the distal end. The electrode has a helical groove on the outer surface. A stripper is arranged at the outer circumference of the electrode which serves to strip off contaminants from the raised surface areas of the electrode and to displace same into the helical groove in which the contaminants are transported to the proximal side. The electrode is closed at its distal end.
DE 696 35 288 T2 discloses electrosurgical electrodes having a silicone coating which prevents the built-up of coagulated tissue on the electrode and which facilitates the removal of coagulated tissue from the electrode.
U.S. Pat. No. 5,460,629 discloses an electrosurgical instrument having two types of electrodes arranged at its distal end, namely a hook-shaped electrode and two plate-shaped electrodes which are arranged on opposite sides of the hook-shaped electrode. The plate-shaped electrodes can be moved axially relative to the hook-shaped electrode, whereby the plate-shaped electrodes strip off coagulated tissue from the sides of the hook-shaped electrode. Thus, the plate-shaped electrodes are only effective on the side surfaces of the hook-shaped electrode.
U.S. Pat. No. 5,451,223 discloses an electrosurgical scalpel having a blade which has a blade cleaning device. The cleaning device is formed by a metal sleeve, the inner cross-section of which is adapted to the outer cross-section of the blade, and the distal opening of which is configured as a sharp blade. By axially moving the sleeve in forward direction, coagulated tissue adhering to the blade is stripped off.
Finally, EP 0 418 382 A1 discloses an electrosurgical instrument having electrodes to which cleaning elements are assigned which are axially movable relative to the electrodes.